Numerous types of apparatus have been developed for exercising a body joint and the associated muscles, tendons, and ligaments. Typically, such devices are composed of a lever arm having one end pivotally mounted on a stationary frame. The device is operated by the extension or flexion of a body limb pushing or pulling on the opposite end of the lever arm. A resistance device is employed to resist the pivoting movement of the lever arm about the location that the lever arm is mounted on the stationary frame. Examples of such exercise devices are disclosed by U.S. Pat. Nos. 2,777,439, 3,495,824, 4,291,787, 4,407,496, 4,436,303, 4,441,708, 4,448,412, 4,493,485, 4,722,525, 4,600,189, 4,621,807, and 4,666,149.
A significant drawback of many of the foregoing exercise devices is that they are cumbersome, composed of a very large number of components, and too expensive for individuals to purchase for use at home (see, for example, the aforementioned '439, '496, '303, '189, '807, and '149 patents). Another serious drawback of the foregoing exercise devices is that they are designed for use with only one type of body limb and thus, are restrictive in their capabilities. For instance, the devices of the aforementioned '787, '708, '412, '485, '189, '807, '149 patents are only adapted to exercise the user's legs. Further, the foregoing exercise devices do not measure any workout parameters or provide the user with feedback concerning the rehabilitative progress being made by the user.
Specialized diagnostic and physical therapy machines have been developed for rehabilitating an injured body joint. The machines have been designed to control and measure the resistance level imparted against the movement of the body limb about its joint. Such machines may also measure the range of movement of the body joint. Due to their size, cost, and complexity, such machines are not practical for individual ownership, and thus are only available at the facilities of a physical therapist or clinic specializing in sports-related injuries. To use these machines, the patient must leave his place of employment or home to travel to the office or clinic of the therapist or sports medicine doctor. Examples of specialized, stationary machines that have been designed for rehabilitating body joints are disclosed in U.S. Pat. Nos. 3,465,592, 4,601,468, and 4,722,525. Other examples of such machines are marketed by Loredan Biomedical, Inc. of Davis, Calif. under the trademarks LIDO.RTM. Active and LIDO.RTM. Digital; the Cybex division of Lumex Inc. of Ronkonkoma, N.Y. under Model Cybex 340 and by Chattex Corporation of Chattanooga, Tenn. under the designation KIN-COM.RTM..